Simulation techniques test automotive cluster display ECUs

With automotive display cluster being the main means to convey the status and information of a vehicle system and drive conditions, it is of utmost importance to ensure reliable functional testing for these cluster devices. This article describes the test coverage for a typical automotive cluster and how these tasks are done through system simulation techniques.

All vehicles are equipped with a panel to display to the driver status and information of the vehicle system and drive conditions. This cluster assembly (also known as dashboard) usually includes a speedometer, tachometer, fuel gauge, temperature gauge, odometer, and a set of telltale warning lamps. In addition, most modern vehicles are also capable of on-board diagnostics enabled by embedded systems connected through communication networks such as controller area network (CAN) and K-line.

All drivers rely on the dashboard for every vital piece of information: When the low fuel indicator lights up, it’s about time to visit the gas station; if the brake warning light remains on even though the handbrake is released, this could indicate insufficient brake fluid and it may be unsafe to use the vehicle. Therefore, a dashboard with guaranteed performance is important to provide a better and safer driving experience.

In the automotive industry, rather than using standard test commands, real loads and real stimuli are "must haves" during the product testing stages as the actual functions of a vehicle depend on these. With these loads and stimuli, clusters need to be correctly tested.

For a novice automotive electronics test engineer, this may well be very challenging as every section on a cluster calls for different sets of inputs or outputs. The door indicator on the dashboard gets input from car doors and has to respond correctly on whether to notify the driver on the status of the doors; the tachometer will be able to display the rate of rotation of the engine’s crankshaft with an engine running.

It might end up that the entire vehicle has to be placed on the production floor just for cluster testing. In manufacturing, production floor space equates to premium real estate, and cost must be well-managed, thus making the above approach unrealistic. In addition, to guarantee the accuracy for every manufacturing test performed, well-calibrated equipment must be used to achieve accurate test results. What should be the design of a practical test system for automotive cluster testing in production?

In manufacturing, most of the end-of-line functional test systems would resemble the standard Agilent TS5000 series system which houses industry-standard equipment. A typical test system will include:

Power supply to represent vehicle battery

Multimeter for voltage and current measurement

Frequency generator to source square waves of various frequencies

Switch/load box and plug-in cards (relay cards)

Instruments simulate dashboard display stimuli

The instruments shown above are the main trunk of a tester in an automotive cluster testing. They are used for powering up, stimulating, switching, and performing measurements by the module.